e20656 Background: Previous studies have shown that cancer patients are at risk of drug interactions. But the proportion of potential adverse events that turn into clinical consequences is unknown. We sought to evaluate how many hospital admissions in oncology are due to drug-drug interactions (DDI) or adverse drug reactions (ADR). Methods: All cancer patients admitted to an oncology ward during an 8-month period had their charts retrospectively evaluated for reasons of hospitalization. Clinical trial patients were excluded. Each hospital admission was independently evaluated by two blinded investigators using a 4-point scale that was developed to classify sadmissions by their probability to be associated with either a DDI or an ADR (definitely, probably, possibly or unlikely associated). All medical records were thoroughly reviewed and discussed by experts. Results: From September 2007 to May 2008, there were 550 hospital admissions and 458 were eligible. Among unplanned admissions (N=298), 39 (13.0%, 95% CI 9.4 - 17.4%) were considered to be associated with an adverse drug event: 33 (11.0%, 95% CI 7.7 - 15.2%) were associated with an ADR and 6 (2.0%, 95% CI 0.7 - 4.3%) with a DDI. The most common DDI involved warfarin, captopril and anti-inflammatory agents and the most frequent ADR was neutropenic fever post chemotherapy. Most patients were discharged completely recovered but 2 patients died. Use of chemotherapy within 4 weeks of hospital admission (Odds Ratio 10.8, 95% CI 5.3 - 22.1; p < 0.0001) and presence of hematological tumors (Odds Ratio 12.1, 95% CI 5.9 - 25; p < 0.0001) were risk factors for being hospitalized to treat an ADR. Conclusions: Approximately one in 10 unplanned hospitalizations of cancer patients is associated with an adverse drug event. Prospective and population-based studies are warranted to evaluate their magnitude in oncology. [Table: see text]
Urgent Hospital Admissions Caused by Adverse Drug Reactions and Medication Errors—A Population-Based Study in Spain